# US 2025/0098541 A1 · Acoustic resonance sensor devices for radical species detection with enhanced filters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0098541 A1 - Document ID: US20250098541A1 - Status: Published application - Kind: A1 - Application number: 18/883,312 - Filed: 2024-09-12 - Published: 2025-03-20 - Earliest claimed: 2023-09-19 - Assignees: Applied Materials, Inc. - Applicants: Applied Materials, Inc. - Inventors: Jia Pelpa; Mehran Moalem; Mehdi Balooch; Damodar Shanbhag - Web page: https://patentgrep.com/patent/US20250098541A1 ## CPC - H10N 30/302: {Sensors} - G01N 29/022: {Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices (microdevices per se B81B)} - G01N 29/036: by measuring frequency or resonance of acoustic waves - G10K 11/04: Acoustic filters {; Acoustic resonators} - H01J 37/32981: {Gas analysis} - H10N 30/03: Assembling devices that include piezoelectric or electrostrictive parts - H10N 30/067: Forming single-layered electrodes of multilayered piezoelectric or electrostrictive parts - H10N 30/082: by etching, e.g. lithography - H10N 30/852: {Composite materials, e.g. having 1-3 or 2-2 type connectivity} - H10N 30/871: {Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes} - G01N 2291/0256: Adsorption, desorption, surface mass change, e.g. on biosensors - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A device can include a radical sensor including a piezoelectric resonator. The radical sensor includes a base structure including a piezoelectric material, and a filter formed on the base structure to selectively react with a radical species. A resonant frequency of the radical sensor changes in response to reaction of the radical species to the filter. The filter includes at least one of: a crystalline material, a doped coating, or a coating having a thickness that ranges from about 5 micrometers to about 50 micrometers. ## Claims ### Claim 1 A device comprising: a radical sensor comprising a piezoelectric resonator, the radical sensor comprising: a base structure comprising a piezoelectric material; and a filter formed on the base structure to selectively react with a radical species, wherein a resonant frequency of the radical sensor changes in response to reaction of the radical species to the filter, and wherein the filter comprises at least one of: a crystalline material, a doped coating, or a coating having a thickness that ranges from about 5 micrometers to about 50 micrometers. ### Claim 2 (depends on 1) The device of claim 1, wherein the piezoelectric material comprises a quartz crystal. ### Claim 3 (depends on 1) The device of claim 1, wherein the piezoelectric resonator is a quartz crystal microbalance (QCM) resonator. ### Claim 4 (depends on 1) The device of claim 1, wherein the crystalline material is a polycrystalline material. ### Claim 5 (depends on 1) The device of claim 1, wherein the crystalline material comprises a grain having a grain size that ranges from about 100 nanometers to about 50 micrometers. ### Claim 6 (depends on 1) The device of claim 1, wherein the filter is formed directly on the piezoelectric material. ### Claim 7 (depends on 1) The device of claim 1, wherein the base structure further comprises a front electrode formed on the piezoelectric material, and wherein the filter is formed on the front electrode. ### Claim 8 (depends on 1) The device of claim 1, wherein the doped coating comprises at least one of SiO2 or SiC doped with at least one of yttrium, phosphorous, or boron. ### Claim 9 (depends on 1) The device of claim 1, wherein the base structure further comprises a mesh formed on a first side of the piezoelectric material, and an electrode formed on a second side of the piezoelectric material opposite the first side, and wherein the filter is formed on the first side of the piezoelectric material. ### Claim 10 A method comprising: obtaining a base structure of a radical sensor comprising a piezoelectric resonator, the base structure comprising a piezoelectric material; and forming, on the base structure, a filter comprising a crystalline material to selectively react with a radical species, wherein a resonant frequency of the radical sensor changes in response to reaction of the radical species to the filter. ### Claim 11 (depends on 10) The method of claim 10, wherein the piezoelectric material comprises a quartz crystal, and wherein the piezoelectric resonator is a quartz crystal microbalance (QCM) resonator. ### Claim 12 (depends on 10) The method of claim 10, wherein forming the filter further comprises depositing the crystalline material directly on the piezoelectric material. ### Claim 13 (depends on 12) The method of claim 12, wherein forming the filter further comprises etching the piezoelectric material using a mesh formed on the piezoelectric material. ### Claim 14 (depends on 10) The method of claim 10, wherein the base structure further comprises a front electrode formed on the piezoelectric material. ### Claim 15 (depends on 14) The method of claim 14, wherein forming the filter further comprises attaching or bonding the crystalline material to a surface of the front electrode. ### Claim 16 (depends on 10) The method of claim 10, wherein the crystalline material comprises a grain having a grain size that ranges from about 100 nanometers to about 50 micrometers. ### Claim 17 A method comprising: obtaining a base structure of a radical sensor comprising a piezoelectric resonator, the base structure comprising a piezoelectric material; and forming, on the base structure, a filter comprising a coating to selectively react with a radical species, wherein a resonant frequency of the radical sensor changes in response to reaction of the radical species to the filter, and wherein forming the filter comprises at least one of: doping an initial coating with a dopant to form the coating, using a base material and the dopant to deposit the coating, forming the coating to have a thickness that ranges from about 5 micrometers to about 50 micrometers, or forming the coating using a deposition process performed at a temperature ranging from about 150° C. to about 450° C. ### Claim 18 (depends on 17) The method of claim 17, wherein the piezoelectric material comprises a quartz crystal, and wherein the piezoelectric resonator is a quartz crystal microbalance (QCM) resonator. ### Claim 19 (depends on 17) The method of claim 17, wherein the base structure further comprises a front electrode, and wherein the filter is formed on the front electrode. ### Claim 20 (depends on 17) The method of claim 17, wherein the dopant comprises at least one of: yttrium, phosphorous, or boron.